FIGS. 6 and 7 are views showing the schematic structure of a stage device built into an exposure apparatus. FIG. 7 shows an A-A section of FIG. 6. A substrate 101 on which a pattern is to be transferred or drawn is held on a substrate chuck (not shown) mounted on a stage 102. The stage 102 is arranged on a stage transport table 103 through stage guides 106 and driven in the Y direction. The stage guides 106 can include mechanical guide mechanisms or static pressure guides. The stage transport table 103 is supported on a stage unit table 105 by three or more support mechanisms 104 so that the influence of deformation of the stage unit table 105 will not be transmitted to the stage transport table 103.
An example of an electromagnetic actuator which drives the stage 102 includes various types, e.g., a type having an iron core at the center of a coil which generates a magnetic field, a Lorentz linear motor, which uses a core-less coil, and the like. In the example shown in FIGS. 6 and 7, a square annular linear motor, which is a Lorentz type linear motor and has a high motor efficiency, is employed.
The electromagnetic actuator is constituted by a stator obtained by winding a coil 108 around a stator support 107, and a movable element which includes magnets 109. When a current is supplied to the coil 108 of the stator with an appropriate phase, the Lorentz force acts on the magnets 109 to generate a thrust in the movable element. The movable element is connected to the stage 102 through a beam 110 and moves together with the stage 102. The stator has at least one coolant channel 111. Joule heat generated by the coil 108 is recovered by a coolant flowing in the coolant channel 111.
A stator outer box 112 is arranged outside the stator to prevent the heat generated by the coil 108 from adversely affecting the peripheral environment. The stator can be supported at its two ends by, e.g., support mechanisms 114. When the stator is to be used as a passive counter mass which moves while canceling a reaction force generated during stage driving, the support mechanisms 114 support the stator such that when the stage 102 moves, the stator can move in the opposite direction.
As shown in FIGS. 6 and 7, in order to allow the movable element to move in the Y direction together with the stage 102, the stator outer box 112 has a slit (opening) 113 which serves as a path of the beam 110 which connects the movable element and stage 102. The slit 113 has a length corresponding to the drive stroke of the stage 102.
As described above, the stator outer box 112 is provided to prevent the heat generated by the coil 108 from being transferred to the peripheral environment. If, however, the slit 113 is arranged at that portion of the constituent portion of the stator outer box 112 which faces the stage 102, the heat generated by the coil 108 adversely affects the temperature distribution in the space (stage space), where the stage 102 is arranged, through the slit 113.
Usually, the light path of a laser interferometer to measure the position of the stage 102 is arranged in the stage space. Temperature fluctuation in the optical path of the laser interferometer decreases the position measurement accuracy of the stage 102 to decrease the positioning accuracy of the stage 102, and the like, thus decreasing the stability of the stage 102. Although a structure on the stage 102 serving as the measurement target of the laser interferometer has a small thermal expansion coefficient, it can deform on the order of nanometers due to a small temperature change. This can also decrease the positioning accuracy of the stage 102, thus decreasing the position reproducibility and overlapping accuracy of a pattern to be formed on the substrate 101.
To prevent heat transfer to the stage space, gas around the coil 108 as the heat portion of the linear motor may be exhausted forcedly. However, the exhaust flow is disordered by the movement of the movable element, and the heat generated by the coil 108 cannot be completely prevented from flowing into the stage space. With this structure, the flow rate necessary for exhaust is very large. This poses a large load to the environment maintaining unit of the exposure apparatus and can lead to an increase in apparatus cost.
In an exposure apparatus, e.g., an EUV (Extreme Ultra Violet) exposure apparatus, which performs exposure in a vacuum or a reduced pressure environment, even if the exposure apparatus is free from the influence of a heat transfer fluid, the influence of radiant heat transfer from the stator coil to the stage space becomes an issue.